Exhaust aftertreatment system

Abstract

The invention relates to an exhaust aftertreatment system. An exhaust aftertreatment system (10) comprises a hydrolysis catalyst (1) and an SCR catalyst (2) disposed downstream of the hydrolysis catalyst (1). The total volume (Vt) of the hydrolysis catalyst (1) and the SCR catalyst (2) for reducing the given amount of NOx is smaller than the volume of the individual SCR catalyst (2) for reducing the given amount of NOx. The vanadium content of the SCR catalyst (2) may be equal to or greater than 0.3%. The hydrolysis catalyst (1) and the SCR catalyst (2) may be configured such that the residence time of the exhaust gas in the SCR catalyst (2) is less than 0.5 seconds, preferably at an engine load of at least 90%. The hydrolysis catalyst (1) and the SCR catalyst (2) may be arranged on the same catalyst substrate (3).

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201911076174.5, titled "Exhaust Aftertreatment System", filed with the State Intellectual Property Office of China on November 6, 2019. Technical Field

[0002] The present invention relates to an exhaust aftertreatment system for an internal combustion engine having at least one cylinder (preferably a large marine engine having at least one cylinder with an inner diameter of at least 200 mm), an internal combustion engine, and a method for reducing NO x emissions of an internal combustion engine.

[0003] The present invention relates to the technical field of internal combustion engines and emission reduction of internal combustion engines.

[0004] The present invention preferably relates to an internal combustion engine, such as a large marine or ship engine or a stationary engine with a cylinder inner diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke crosshead engine. The engine can be a diesel engine, a gas engine, a dual-fuel engine, or a multi-fuel engine. In such an engine, combustion of liquid and / or gaseous fuels, as well as spontaneous or forced ignition, are possible. Background Art

[0005] The internal combustion engine can be a longitudinally scavenged two-stroke engine.

[0006] The term internal combustion engine also refers to a large engine that can operate in a diesel mode characterized by fuel spontaneous combustion and / or in an Otto mode characterized by fuel active ignition. In addition, the term internal combustion engine particularly includes dual-fuel engines and large engines in which fuel spontaneous combustion is used for active ignition of another fuel.

[0007] The engine speed is preferably lower than 800 RPM (4-stroke), more preferably lower than 200 RPM (2-stroke), which represents the name of a low-speed engine.

[0008] The fuel can be diesel, marine diesel, heavy fuel oil, emulsion, slurry, methanol, ethanol, and gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG).

[0009] Other possible fuels that can be added as required are: LBG (liquefied biogas), biofuels (such as oils made from algae), hydrogen, fuels synthesized from CO 2 (such as produced by Power-To-Gas or Power-To-Liquid).

[0010] Large ships, especially cargo ships, are usually powered by internal combustion engines, especially diesel engines and / or gas engines, mostly two-stroke crosshead engines. In the case of engines burning liquid fuels (such as heavy fuel oil, marine diesel oil, diesel or other liquids) as well as gaseous fuels (such as LNG, LPG or others), it is necessary to clean the exhaust gas during this combustion process to comply with existing regulations, such as IMO Tier III.

[0011] IMO emission standards are usually referred to as Tier I... III standards, which specifically define the NO x emission standards for existing and new marine engines.

[0012] For large ships, emission requirements have been increasing, especially regarding nitrogen oxide emissions. Therefore, it is necessary to reduce the amount of nitrogen oxides in the exhaust gas emitted by the internal combustion engines of these ships.

[0013] SCR (Selective Catalytic Reduction) technology is used to reduce the level of nitrogen oxides (NO x ) in the exhaust gas of internal combustion engines. SCR is usually used for land-based engines, such as heavy vehicles, industrial plants and other applications. SCR technology is also applied in the marine environment together with two-stroke diesel engines. Due to the regulatory requirements for said marine diesel engines and land-based engines, the demand for efficient SCR systems is increasing.

[0014] SCR can be based on the reduction of nitrogen oxides in the exhaust gas with ammonia (NH 3 ). Usually, ammonia is generated by injecting an ammonia precursor substance (such as urea solution) into the exhaust gas of the internal combustion engine. For example, the urea solution is sprayed into the hot exhaust gas through a nozzle, and the liquid urea solution reacts here to become ammonia, carbon dioxide and water vapor. Then, under the influence of the catalyst in the SCR reactor, ammonia reduces the nitrogen oxides to nitrogen (N 2 ) and water (H 2 O). The generation of ammonia from liquid urea is endothermic. Therefore, if the exhaust gas is hot enough, only the decomposition of the urea solution is completed, and the nitrogen oxides (NO x ) are only reduced to nitrogen (N 2 ).

[0015] EP3149298B1 discloses a post-treatment system in which a hydrolysis catalytic converter is designated as a dosing device for adding an ammonia precursor substance. Through the hydrolysis catalytic converter, the process of converting the ammonia precursor substance into ammonia upstream of the SCR catalyst can be improved or promoted.

[0016] One problem with known SCR reactors in internal combustion engines is to sufficiently reduce NO xContent. Therefore, a large-capacity SCR reactor is required, in which the exhaust gas has sufficient residence time. A large-capacity SCR reactor requires a large amount of space and is costly.

[0017] The catalysts commonly used in SCR technology either include vanadium and tungsten supported on TiO 2 or are metal-substituted zeolites, such as copper / zeolite or iron / zeolite. Vanadium promotes the oxidation of NO x . However, the vanadium content must be kept at a low level because otherwise, at high engine loads and corresponding high temperatures, SO 2 is oxidized to SO 3 , and when the concentration exceeds a certain level, SO 3 produces a sulfuric acid blue plume in and downstream of the chimney, which must be prevented at all costs. A higher vanadium content may also cause NH 3 to be oxidized to NO x at temperatures above 350 °C. Therefore, more reducing agent must be injected. In addition, a higher vanadium content, especially the combination of vanadium and tungsten, promotes an increase in N 2 O production at temperatures above 350 °C.

[0018] Therefore, the object of the present invention is to prevent the defects of the prior art and create an exhaust gas aftertreatment system, an internal combustion engine, and a method for reducing NO x emissions of an internal combustion engine to ensure reduced operating costs, a smaller size of the aftertreatment system, minimization of side reaction products (such as N 2 O and SO 3 ) emissions and / or a reduction in the dosage of reducing agents (such as ammonia or ammonia precursor substances). Summary of the Invention

[0019] According to a first aspect of the present invention, there is provided an exhaust gas aftertreatment system for an internal combustion engine having at least one cylinder, preferably a large marine engine having at least one cylinder with an inner diameter of at least 200 mm. The exhaust gas aftertreatment system includes a hydrolysis catalyst and an SCR catalyst disposed downstream of the hydrolysis catalyst.

[0020] The total volume of the hydrolysis catalyst and the SCR catalyst for reducing a given amount of NO x is smaller than the volume of a separate SCR catalyst for reducing a given amount of NO x . Preferably, the total volume of the hydrolysis catalyst and the SCR catalyst is less than 400 l / MW.

[0021] The SCR catalyst may be disposed in an SCR reactor. The hydrolysis catalyst may be disposed in a hydrolysis catalytic reactor.

[0022] The SCR catalyst and the hydrolysis catalyst may be disposed in a common reactor.

[0023] Alternatively or as an option, the vanadium content of the SCR catalyst is greater than or equal to 0.3%, preferably greater than or equal to 0.5%, more preferably greater than or equal to 0.7%.

[0024] The percentage refers to the total weight of the catalyst coating.

[0025] Alternatively or as an option, the hydrolysis catalyst and the SCR catalyst are configured to preferably have the residence time of the exhaust gas in the SCR catalyst less than 0.5 seconds, more preferably less than 0.3 seconds, when the engine load is at least 90% and / or the exhaust gas mass flow rate is 2 to 20 kg / kWh, preferably 7 to 11 kg / kWh.

[0026] In particular, the volumes of the hydrolysis catalyst and the SCR catalyst are adjusted in order to achieve a shorter residence time at full load.

[0027] Alternatively or as an option, the hydrolysis catalyst and the SCR catalyst are provided on the same catalyst substrate.

[0028] The SCR catalyst preferably contains vanadium, tungsten and / or TiO 2 , preferably TiO doped with vanadium and tungsten 2 .

[0029] The hydrolysis catalyst not only helps to hydrolyze HNCO into NH 3 , but also helps to decompose urea molecules into HNCO and NH 3 . In addition, at the exhaust gas temperature present at high loads, hydrolysis occurs not only within the hydrolysis catalyst, but also side reactions similar to the SCR reaction occur, in which NO x is significantly reduced.

[0030] Therefore, all the NO x that has been reduced in the hydrolysis catalyst will not be present in the SCR catalyst provided downstream of the hydrolysis catalyst. Therefore, the SCR catalyst only needs to reduce a smaller amount of NO x .

[0031] Therefore, for the same NO x reduction, the volume required for the complete catalytic system comprising the hydrolysis catalyst and the SCR catalyst is less than the volume required for a separate SCR catalyst. Compared with a separate SCR catalyst, the total volume of the catalyst can be reduced by at least 8% to 10%.

[0032] In the present invention, the volume of the catalyst is understood as the cladding volume of the catalyst.

[0033] Since the SCR catalyst only needs to reduce a smaller amount of NO x, so when combined with a hydrolysis catalyst, the SCR catalyst may be smaller in volume, and / or the reaction time may be shorter, and thus the residence time in the SCR catalyst may be shorter.

[0034] Since the exhaust gas may only stay in the SCR catalyst for a short time, for a large separate SCR catalyst, the vanadium content of the SCR catalyst may be high because the reaction time for oxidizing SO 2 and the time for generating N 2 O are also less. In addition, a small SCR catalyst with a high vanadium content can provide the same NO x oxidation rate as a large SCR catalyst with a low vanadium content.

[0035] Only a small part of NH 3 is oxidized in the SCR catalyst, while the main part of NH 3 is effectively utilized. Therefore, only a lower amount of NH 3 needs to be provided. The risk of providing excessive NH 3 can be reduced. NH 3 may be oxidized to NO x in the SCR catalyst, or become ammonia leakage. Excess urea can be prevented.

[0036] For low engine loads and corresponding lower temperatures, the largest part of the "SCR reaction", and thus the largest part of the reduction of NO x occurs in the SCR catalyst. However, during lower load periods, the hydrolysis catalyst at least provides the hydrolysis of HNCO to NH 3 , so that this reaction does not have to occur in the SCR catalyst and no space needs to be provided for hydrolysis in the SCR catalyst. Since the hydrolysis catalyst also contributes to the decomposition of urea, so that almost all of the injected urea exists in the form of NH 3 at the inlet of the SCR catalyst, no additional volume needs to be provided in the SCR catalyst.

[0037] Especially for lower loads, an SCR catalyst containing a high vanadium content (i.e., greater than 0.3%, preferably greater than or equal to 0.5%, more preferably greater than or equal to 0.7%) has very high activity. Therefore, a small SCR catalyst can also achieve the same performance as a large SCR catalyst with a lower vanadium content.

[0038] When operating at a higher engine load, the hydrolysis catalyst can still hydrolyze HNCO to NH 3 , but provides most of the NO x reduction. Only a small amount of NO x not reduced in the hydrolysis catalyst will be reduced in the SCR catalyst.

[0039] When a hydrolysis catalyst and an SCR catalyst are configured as a unit, for example, by being provided on the same catalyst substrate, a more compact arrangement can be achieved. The exhaust gas can flow directly from the hydrolysis catalyst to the SCR catalyst.

[0040] The catalyst substrate can be metallic or ceramic. The substrate can be coated. For example, the inlet of the catalytic unit can be coated only with TiO 2 while the downstream part of the substrate is coated with vanadium, tungsten, and TiO 2 coating.

[0041] In an advantageous embodiment, the exhaust gas aftertreatment system includes NO x sensors, preferably two NO x sensors.

[0042] The exhaust gas aftertreatment system can particularly include three NO x sensors, the first being provided upstream of the hydrolysis catalyst, the second being provided downstream of the hydrolysis catalyst and upstream of the SCR catalyst, and the third being provided downstream of the SCR catalyst.

[0043] Preferably, the NO x sensors are provided downstream of the hydrolysis catalyst and / or downstream of the SCR catalyst. The NO x sensors can also be provided upstream of the hydrolysis catalyst.

[0044] By measuring the NO x content at different stages of the exhaust gas aftertreatment system, the effectiveness of each part can be monitored.

[0045] Sensors that collect data allowing conclusions to be drawn about the NO x content can be used instead of the NO x sensors.

[0046] Preferably, the exhaust gas aftertreatment system includes a control unit for comparing the measured NO x value or the difference between the NO x values measured at different stages with a reference value. Measures can be taken based on the result of the comparison. For example, the amount of the injected reducing agent (such as ammonia or an ammonia precursor substance such as urea) can be changed, or the temperature of at least a part of the exhaust gas aftertreatment system can be changed, or more or less additional fuel consumption must be provided.

[0047] As an option, when the control unit indicates that a sufficient amount of NO x has been reduced in the hydrolysis catalyst, the SCR catalyst can be bypassed, or only a part of the exhaust gas is guided through the SCR catalyst.

[0048] Depending on the applicable rules, fuel type, engine power level, and other factors, different systems are required to handle the exhaust gas. Thus, in the exhaust system of a marine engine, the exhaust gas can be diverted in different directions.

[0049] In a preferred embodiment of the present invention, the exhaust gas aftertreatment system includes at least one bypass separation device upstream of the hydrolysis catalyst. At least one first bypass exhaust gas pipeline and at least one second bypass exhaust gas pipeline are connected to the at least one bypass separation device. The at least one bypass separation device is configured to separate the exhaust gas upstream of the hydrolysis catalyst into a first gas flow for the first bypass exhaust gas pipeline and a second gas flow for the second bypass exhaust gas pipeline. The hydrolysis catalyst and the SCR catalyst are disposed in the first bypass exhaust gas pipeline downstream of the bypass separation device.

[0050] Therefore, a bypass is provided that provides a branch of at least a portion of the exhaust gas such that this portion does not enter the hydrolysis catalyst and the SCR catalyst.

[0051] The first bypass exhaust gas pipeline and the second bypass exhaust gas pipeline can converge downstream of the SCR catalyst, so that the first and second gas flows are combined in one pipeline.

[0052] Preferably, the exhaust gas aftertreatment system includes a bypass regulating device for setting the throughput of the first bypass exhaust gas pipeline and the second bypass exhaust gas pipeline.

[0053] The bypass regulating device can be implemented by at least one bypass regulating valve for opening and closing the first bypass exhaust gas pipeline and / or the second bypass exhaust gas pipeline. The first bypass exhaust gas pipeline and the second bypass exhaust gas pipeline can each have a valve. Thus, the required proportion of the total exhaust gas leaving the cylinder can be directed through the first bypass exhaust gas pipeline and thus through the hydrolysis catalyst and the SCR catalyst.

[0054] The complete catalytic system including the hydrolysis catalyst and the SCR catalyst can be separated, for example, in Tier II mode, which is defined as the case where a higher NO x level is considered acceptable such that all of the exhaust gas does not pass through the hydrolysis catalyst and the SCR catalyst.

[0055] Advantageously, the exhaust gas aftertreatment system includes a control unit for controlling the throughput of the first bypass exhaust gas pipeline and the second bypass exhaust gas pipeline, preferably depending on the NO x value, temperature, and / or engine load.

[0056] Depending on the performance of the entire system, it can be determined, for example, by measuring the NO x value downstream of the SCR catalyst or downstream of the confluence of the first and second gas flows, and / or depending on the required performance, more or less of the exhaust gas is conducted through the first bypass exhaust gas pipeline and / or the second bypass exhaust gas pipeline.

[0057] In a preferred embodiment of the present invention, the exhaust aftertreatment system includes at least one conductive separation device downstream of the hydrolysis catalyst. A first conductive exhaust pipe line and a second conductive exhaust pipe line are connected to the at least one conductive separation device. The at least one conductive separation device is configured to separate the exhaust gas leaving the hydrolysis catalyst into a first gas stream for the first conductive exhaust pipe line and a second gas stream for the second conductive exhaust pipe line. An SCR catalyst is provided in the first conductive exhaust pipe line downstream of the conductive exhaust device.

[0058] Accordingly, a bypass is provided which provides a branch of at least a portion of the exhaust gas leaving the hydrolysis catalyst such that this portion does not enter the SCR catalyst.

[0059] The first conductive exhaust pipe line and the second conductive exhaust pipe line may converge downstream of the SCR catalyst so that the first and second gas streams are combined in one pipe line.

[0060] If the hydrolysis catalyst is large enough to completely reduce NO x to Tier III levels at high engine loads, then the SCR catalyst is not required. The conductive separation device downstream of the hydrolysis catalyst allows bypassing of the SCR catalyst.

[0061] Preferably, the exhaust aftertreatment system includes a conductive regulating device for setting the throughput of the first conductive exhaust pipe line and the second exhaust pipe line. In particular, the conductive regulating device includes at least one conductive regulating valve for opening and closing the first conductive exhaust pipe line and / or the second conductive exhaust pipe line. Each of the first conductive exhaust pipe line and the second conductive exhaust pipe line has a valve.

[0062] Accordingly, a desired proportion of the exhaust gas leaving the hydrolysis catalyst can be directed through the first conductive exhaust pipe line and thus through the SCR catalyst.

[0063] The conductive separation device downstream of the hydrolysis catalyst allows the SCR catalyst to be used, for example, only at lower engine loads.

[0064] Advantageously, the exhaust aftertreatment system includes a control unit for controlling the throughput of the first conductive exhaust pipe line and the second conductive exhaust pipe line preferably according to the NO x value, temperature and / or engine load.

[0065] If the NO x value measured downstream of the SCR catalyst or downstream of the confluence of the first and second gas streams exceeds a given value, or if the NO x value measured upstream of the hydrolysis catalyst and the NO xIf the difference in values is below a predetermined value, the performance may be considered too small. In this case, the control unit can be triggered to open the first conductive exhaust gas pipeline and / or enhance the first air flow.

[0066] The exhaust gas aftertreatment system may include a bypass separation device and a conductive separation device. The second bypass exhaust gas pipeline can be merged with the second conductive exhaust gas pipeline and the first conductive exhaust gas pipeline, and the second bypass exhaust gas pipeline can converge downstream of the SCR catalyst, so that the air flows are merged.

[0067] The control unit can control the throughput through the first bypass exhaust gas pipeline, the second bypass exhaust gas pipeline, the second conductive exhaust gas pipeline, and the second exhaust gas pipeline.

[0068] According to a second aspect of the present invention, there is provided an exhaust gas aftertreatment system for an internal combustion engine of at least one cylinder, preferably a large marine engine having at least one cylinder with an inner diameter of at least 200 mm, preferably as described above. The exhaust gas aftertreatment system includes a hydrolysis catalyst, and the hydrolysis catalyst can reduce the NO in the hydrolysis catalyst by at least 5%, preferably at least 10%, more preferably at least 20% when the temperature is at least 420 °C and / or the engine load is at least 90% and / or the exhaust gas mass flow rate is 2 - 20 kg / kWh, preferably 7 - 11 kg / kWh. The size of the hydrolysis catalyst is preferably such that the required performance is achieved in terms of NO reduction. x concentration by at least 5%, preferably at least 10%, more preferably at least 20%. The size of the hydrolysis catalyst is preferably such that the required performance is achieved in terms of NO x reduction.

[0069] The hydrolysis catalyst may include TiO 2 and / or ZrO 2 and / or Al 2 O 3 and / or SiO 2 and / or H-ZSM-5.

[0070] The exhaust gas aftertreatment system may include a dosing unit for a reducing agent such as ammonia or an ammonia precursor substance (such as urea). The dosing unit can also be arranged upstream of the exhaust gas aftertreatment system.

[0071] The object of the present invention is also achieved by an internal combustion engine of at least one cylinder, preferably a large marine engine having at least one cylinder with an inner diameter of at least 200 mm, including the exhaust gas aftertreatment system as described above.

[0072] The object of the present invention is also achieved by a method for reducing NO x emissions of an internal combustion engine (preferably the internal combustion engine as described above). The method includes the following steps. The exhaust gas is discharged through the cylinder outlet. Preferably, a reducing agent such as ammonia or an ammonia precursor substance (such as urea) is dosed into the exhaust gas. Alternatively, an aqueous ammonia solution, a urea solution, an ammonium carbonate solution, ammonium carbamate, or urea powder can also be dosed.

[0073] The exhaust gas is guided to a hydrolysis catalyst, and NO in the hydrolysis catalyst is reduced by at least 5%, preferably at least 10%, more preferably at least 20% when the temperature is at least 420 °C and / or the engine load is at least 90% and / or the exhaust gas mass flow rate is 2 - 20 kg / kWh, preferably 7 - 11 kg / kWh. x concentration is reduced by at least 5%, preferably at least 10%, more preferably at least 20%.

[0074] The object of the present invention is also achieved by a method for reducing NO x emissions of an internal combustion engine (preferably an internal combustion engine as described above), preferably the method as described above. The method comprises the following steps.

[0075] The exhaust gas is discharged through the cylinder outlet. Preferably, a substance reducing agent is metered into the exhaust gas.

[0076] Preferably, the throughput of the first bypass exhaust pipe line and the second bypass exhaust pipe line is controlled according to the measured NO x value, temperature and / or engine load. The first bypass exhaust pipe line and the second bypass exhaust pipe line are connected to at least one conduction separation device provided upstream of the hydrolysis catalyst. The hydrolysis catalyst is provided in the first bypass exhaust pipe line, and the second bypass exhaust pipe line bypasses the hydrolysis catalyst.

[0077] In particular, an SCR catalyst is provided downstream of the hydrolysis catalyst, and the SCR catalyst is provided in the first bypass exhaust pipe line so that the second bypass exhaust pipe line also bypasses the SCR catalyst.

[0078] The object of the present invention is also achieved by a method for reducing NO x emissions of an internal combustion engine (preferably an internal combustion engine as described above), preferably the method as described above. The method comprises the following steps:

[0079] The exhaust gas is discharged through the outlet of the cylinder. Preferably, a substance reducing agent is metered into the exhaust gas.

[0080] At least a part of the exhaust gas is guided to the hydrolysis catalyst.

[0081] Preferably, the throughput of the first conduction exhaust pipe line and the second conduction exhaust pipe line is controlled according to the measured NO x value, temperature and / or engine load.

[0082] The first conduction exhaust pipe line and the second conduction exhaust pipe line are connected to at least one conduction separation device provided downstream of the hydrolysis catalyst. The SCR catalyst is provided in the first conduction exhaust pipe line, and the second conduction exhaust pipe line bypasses the SCR catalyst.

[0083] The object of the present invention is also achieved by a method for reducing NO xThe emission method is implemented, preferably by the method described above. The method comprises the following steps:

[0084] The exhaust gas is discharged through the outlet of the cylinder. Preferably, a substance reducing agent is dosed into the exhaust gas. The exhaust gas is guided through a hydrolysis catalyst. The exhaust gas is guided through an SCR catalyst arranged downstream of the hydrolysis catalyst.

[0085] An exhaust gas aftertreatment system is used, wherein the total volume of the hydrolysis catalyst and the SCR catalyst for reducing a given amount of NO x is less than the volume of a separate SCR catalyst for reducing a given amount of NO x Preferably, the total volume of the hydrolysis catalyst and the SCR catalyst is less than 500 l / MW, preferably 400 l / MW.

[0086] Alternatively or as an option, the vanadium content of the SCR catalyst is equal to or greater than 0.3%, preferably equal to or greater than 0.5%, more preferably equal to or greater than 0.7%.

[0087] Alternatively or as an option, the hydrolysis catalyst and the SCR catalyst are configured to preferably cause the residence time of the exhaust gas in the SCR catalyst to be less than 0.5 seconds, preferably less than 0.3 seconds, when the engine load is at least 90% and / or the exhaust gas mass flow rate is 2 - 20 kg / kWh, preferably 7 - 11 kg / kWh.

[0088] Alternatively or as an option, the hydrolysis catalyst and the SCR catalyst are arranged on the same catalyst substrate.

[0089] In a preferred embodiment of the present invention, the NO x content in the exhaust gas is measured.

[0090] The NO x content can be measured upstream of the hydrolysis catalyst and / or downstream of the hydrolysis catalyst and / or downstream of the SCR catalyst.

[0091] Advantageously, the measured NO x content is compared with a reference value. The reference value can be a given value, for example, the NO x emission value according to applicable rules.

[0092] The reference value can also be a measured value. For example, the NO x value measured downstream of the hydrolysis catalyst can be compared with the NO x value measured upstream of the hydrolysis catalyst.

[0093] Depending on the comparison, more or less exhaust gas can be guided through the hydrolysis catalyst and / or the SCR catalyst. Description of the Drawings

[0094] The present invention will be further described in detail in the embodiments with reference to the accompanying drawings:

[0095] Figure 1 A schematic diagram showing a first embodiment of an internal combustion engine;

[0096] Figure 2 A schematic diagram showing a second embodiment of an internal combustion engine;

[0097] Figure 3 A schematic diagram showing a third embodiment of an internal combustion engine. Detailed implementation manners

[0098] Figure 1 A schematic diagram showing a first embodiment of the internal combustion engine 10.

[0099] The internal combustion engine 20 may have four cylinders 21, and the inner diameter 27 of each cylinder 21 is at least 200 mm.

[0100] The exhaust gas is discharged through the outlet 7.

[0101] The internal combustion engine 20 includes an exhaust gas aftertreatment system 10 having a hydrolysis catalyst 1 and an SCR catalyst 2 disposed downstream of the hydrolysis catalyst 1.

[0102] The vanadium content of the SCR catalyst 2 may be equal to or greater than 0.3%.

[0103] The exhaust gas aftertreatment system 10 includes two NO x sensors 4 and 5. The first NO x sensor 4 is disposed downstream of the SCR catalyst 2. The second NO x sensor 5 is disposed upstream of the hydrolysis catalyst 1. Other NO x sensors not shown in the figure may be disposed between the hydrolysis catalyst 1 and the SCR catalyst 2.

[0104] The exhaust gas aftertreatment system 10 includes a control unit 6 for comparing the NO x value measured by the first NO x sensor 4 and the NO x value measured by the second NO x sensor 5 or the NO x value measured by other NO x sensors to check the performance of the hydrolysis catalyst 1 and the SCR catalyst 2.

[0105] The control unit 6 is also suitable for determining the load of the engine based on the speed and fuel command.

[0106] The exhaust gas aftertreatment system 10 includes a bypass separation device 17 upstream of the hydrolysis catalyst 1. A first bypass exhaust gas pipeline 18 and a second bypass exhaust gas pipeline 19 are connected to the bypass separation device 17.

[0107] The bypass separation device 17 is configured to separate the exhaust gas downstream of the hydrolysis catalyst 1 into a first gas flow for the first bypass exhaust gas pipeline 18 and a second gas flow for the second bypass exhaust gas pipeline 19.

[0108] The first bypass exhaust gas pipeline 18 and the second bypass exhaust gas pipeline 19 may be combined, and the exhaust gas may be guided to the turbocharger 26. An additional valve 25 provided downstream of the SCR catalyst may close the first bypass exhaust gas pipeline 18 to prevent the exhaust gas from flowing into the SCR catalyst through the second bypass exhaust gas pipeline 19.

[0109] The hydrolysis catalyst 1 and the SCR catalyst 2 are provided in the first bypass exhaust gas pipeline 18 downstream of the bypass separation device 17.

[0110] The exhaust gas aftertreatment system 10 includes a bypass adjustment device 22 for setting the throughput of the first bypass exhaust gas pipeline 18 and the second bypass exhaust gas pipeline 19.

[0111] The bypass adjustment device 22 includes a first bypass regulating valve 23 for opening and closing the first bypass exhaust gas pipeline 18, and a second bypass regulating valve 24 for opening and closing the second bypass exhaust gas pipeline 19.

[0112] The internal combustion engine 20 may include a temperature sensor not shown in the figure.

[0113] According to the NO x reduction performance, the measured NO x value, temperature, and / or engine load, the control unit 6 can control the throughput of the first bypass exhaust gas pipeline 18 and the second bypass exhaust gas pipeline 19 by sending signals for opening and / or closing the first bypass regulating valve 23 and the second bypass regulating valve 24.

[0114] Figure 2 A schematic diagram showing a second embodiment of the internal combustion engine 10 is shown. The internal combustion engine 20 may have four cylinders 21.

[0115] The internal combustion engine 20 includes an exhaust gas aftertreatment system 10 having a hydrolysis catalyst 1 and an SCR catalyst 2 provided downstream of the hydrolysis catalyst 1.

[0116] The exhaust gas aftertreatment system 10 includes a conduction separation device 11 downstream of the hydrolysis catalyst 1, wherein a first conduction exhaust gas pipeline 12 and a second conduction exhaust gas pipeline 13 are connected to at least one conduction separation device 11.

[0117] The conduction separation device 11 is configured to separate the exhaust gas leaving the hydrolysis catalyst 1 into a first gas stream for the first conduction exhaust pipe line 12 and a second gas stream for the second conduction exhaust pipe line 13. The SCR catalyst 2 is provided in the first conduction exhaust pipe line 12 downstream of the conduction separation device 11.

[0118] The exhaust gas aftertreatment system 10 includes an adjustment device 14 for setting the throughput of the first conduction exhaust pipe line 12 and the second conduction exhaust pipe line 13. The adjustment device 14 includes a first conduction regulating valve 15 for opening and closing the first conduction exhaust pipe line 12, and a second conduction regulating valve 16 for opening and closing the second conduction exhaust pipe line 13.

[0119] The exhaust gas aftertreatment system 10 may include two NO x sensors 4 and 8. The first NO x sensor 4 is provided downstream of the SCR catalyst 2. The second NO x sensor 8 is provided downstream of the hydrolysis catalyst 1.

[0120] Other sensors not shown in the figure may be provided upstream of the hydrolysis catalyst 1.

[0121] The exhaust gas aftertreatment system 10 includes a control unit 6 for controlling the throughput of the first conduction exhaust pipe line 12 and the second conduction exhaust pipe line 13. For example, according to the NO x value measured by the second NO x sensor 8 (which is a measurement of the NO x reduction performance of the hydrolysis catalyst 1), the control unit may send signals for opening and closing the first conduction regulating valve 15 and the conduction second regulating valve 16.

[0122] The control unit may also send signals for opening and / or closing the first bypass regulating valve 23 and the second bypass regulating valve 24 so that at least a part of the exhaust gas can bypass the hydrolysis catalyst 1 and the SCR catalyst 2.

[0123] Figure 3 A schematic diagram showing a third embodiment of the internal combustion engine 20 is shown. The internal combustion engine 20 may have four cylinders 21.

[0124] The internal combustion engine 20 includes an exhaust gas aftertreatment system 10 having a hydrolysis catalyst 1 and an SCR catalyst 2 provided downstream of the hydrolysis catalyst 1.

[0125] The hydrolysis catalyst 1 and the SCR catalyst 2 are provided on the same catalyst substrate 3.

[0126] The total volume V x of the hydrolysis catalyst 1 and the SCR catalyst 2 for reducing a given amount of NO t is equal to or less than that for reducing a given amount of NOx Volume of the individual SCR catalyst. The total volume V of the hydrolysis catalyst 1 and the SCR catalyst 2 t is equal to or less than 500 l / MW, preferably 400 l / MW.

Claims

1. An exhaust gas aftertreatment system (10) for an internal combustion engine (20) having at least one cylinder (21), preferably a large marine engine having at least one cylinder (21) with an inner diameter (27) of at least 200 mm, The exhaust gas aftertreatment system (10) includes a hydrolysis catalyst (1) and an SCR catalyst (2) preferably including vanadium- and tungsten-doped TiO 2 disposed downstream of the hydrolysis catalyst (1), wherein - For reducing a given amount of NO x The total volume (V t ) of the hydrolysis catalyst (1) and the SCR catalyst (2) for reducing a given amount of NO x is less than the volume of a separate SCR catalyst (2) for reducing a given amount of NO t , preferably, the total volume (V ) is less than 500 l / MW, preferably 400 l / MW and / or - the vanadium content of the SCR catalyst (2) is equal to or greater than 0.3%, preferably equal to or greater than 0.5%, more preferably equal to or greater than 0.7%, and / or - the hydrolysis catalyst (1) and the SCR catalyst (2) are configured such that, preferably when the engine load is at least 90% and / or the exhaust gas mass flow rate is 2 to 20 kg / kWh, preferably 7 to 11 kg / kWh, the residence time of the exhaust gas in the SCR catalyst (2) is less than 0.5 seconds, preferably less than 0.3 seconds, and / or - the hydrolysis catalyst (1) and the SCR catalyst (2) are provided on the same catalyst substrate (3).

2. The exhaust gas aftertreatment system (10) according to claim 1, wherein the exhaust gas aftertreatment system (10) comprises NO x sensors (4, 5, 8), preferably two NO x sensors (4, 5, 8).

3. The exhaust gas aftertreatment system (10) according to claim 2, wherein the exhaust gas aftertreatment system (10) comprises a control unit (6) for comparing the measured NO x value with a reference value.

4. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 3, wherein the exhaust gas aftertreatment system (10) includes at least one bypass separation device (17) upstream of the hydrolysis catalyst (1), - wherein a first bypass exhaust gas pipeline (18) and a second bypass exhaust gas pipeline (19) are connected to the at least one bypass separation device (17), - wherein the at least one bypass separation device (17) is configured to separate the exhaust gas upstream of the hydrolysis catalyst (1) into a first gas flow for the first bypass exhaust gas pipeline (18) and a second gas flow for the second bypass exhaust gas pipeline (19), and - wherein the hydrolysis catalyst (1) and the SCR catalyst (2) are provided in the first bypass exhaust gas pipeline (18) downstream of the bypass separation device (17).

5. The exhaust gas aftertreatment system (10) according to claim 4, wherein the exhaust gas aftertreatment system (10) includes a bypass adjustment device (22) for setting the throughput of the first bypass exhaust gas pipeline (18) and the second bypass exhaust gas pipeline (19), preferably at least one bypass regulating valve (23, 24) for opening and closing the first bypass exhaust gas pipeline (18) and / or the second bypass exhaust gas pipeline (19).

6. The exhaust gas aftertreatment system (10) according to claim 4 or 5, wherein the exhaust gas aftertreatment system (10) comprises a control unit (6) for controlling the throughput of the first bypass exhaust pipe line (18) and the second bypass exhaust pipe line (19), preferably according to the NO x value, temperature and / or engine load.

7. The exhaust gas aftertreatment system (10) according to any one of claims 1 to 6, wherein the exhaust gas aftertreatment system (10) includes at least one conduction separation device (11) downstream of the hydrolysis catalyst (1) - wherein a first conduction exhaust gas pipeline (12) and a second conduction exhaust gas pipeline (13) are connected to the at least one conduction separation device (11), - wherein the at least one conduction separation device (11) is configured to separate the exhaust gas leaving the hydrolysis catalyst (1) into a first gas flow for the first conduction exhaust gas pipeline (12) and a second gas flow for the second conduction exhaust gas pipeline (13), and - wherein the SCR catalyst (2) is provided in the first conduction exhaust gas pipeline (12) downstream of the conduction exhaust device (11).

8. The exhaust gas aftertreatment system (10) according to claim 7, wherein the exhaust gas aftertreatment system (10) comprises a conduction regulating device (14) for setting the throughput of the first conduction exhaust pipe line (12) and the second conduction exhaust pipe line (13), preferably comprising at least one conduction regulating valve (15, 16) for opening and closing the first conduction exhaust pipe line (12) and / or the second conduction exhaust pipe line (13).

9. The exhaust gas aftertreatment system (10) according to claim 7 or 8, wherein the exhaust gas aftertreatment system (10) comprises a control unit (6) for controlling the throughput of the first conductive exhaust pipe line (12) and the second conductive exhaust pipe line (13), preferably as a function of the NO x value, the temperature and / or the engine load.

10. Preferably, the exhaust gas aftertreatment system (10) according to any one of claims 1 to 9, the exhaust gas aftertreatment system (10) being for an internal combustion engine (20) having at least one cylinder (21), preferably a large marine engine having at least one cylinder (21) with an inner diameter (27) of at least 200 mm. The exhaust aftertreatment system (10) includes a hydrolysis catalyst (1), and the hydrolysis catalyst (1) can reduce the NO concentration in the hydrolysis catalyst (1) by at least 5%, preferably at least 10%, more preferably at least 20% when the temperature is at least 420 °C and / or the engine load is at least 90% and / or the exhaust mass flow rate is 2-20 kg / kWh, preferably 7-11 kg / kWh. x Concentration is reduced by at least 5%, preferably at least 10%, more preferably at least 20%.

11. An internal combustion engine (20) having at least one cylinder (21), preferably a large marine engine having at least one cylinder (21) with an inner diameter (27) of at least 200 mm, the internal combustion engine comprising the exhaust gas aftertreatment system (10) according to any one of claims 1 to 10.

12. A method for reducing NO x emissions of an internal combustion engine, which is preferably the internal combustion engine described in claim 11, the method Comprising the following steps: - Discharging exhaust gas through the outlet (7) of the cylinder (21). - Guide the exhaust gas to the hydrolysis catalyst (1) and reduce the NO concentration in the hydrolysis catalyst (1) by 5%, preferably at least 10%, more preferably at least 20% when the temperature is at least 420 °C and / or the engine load is at least 90% and / or the exhaust gas mass flow rate is 2 - 20 kg / kWh, preferably 7 - 11 kg / kWh. x Concentration is reduced by 5%, preferably at least 10%, more preferably at least 20%.

13. Preferably, the method for reducing NOx emissions from an internal combustion engine as described in claim 12, wherein the internal combustion engine is preferably the internal combustion engine as described in claim 11, and the exhaust gas is discharged through the outlet (7) of the cylinder (21), the method x wherein the exhaust gas is discharged through the outlet (7) of the cylinder (21), the method Comprising the following steps: - Preferably according to the measured NO x value, temperature and / or engine load, control the throughput of the first bypass exhaust pipe line (18) and the second bypass exhaust pipe line (19), wherein the first bypass exhaust pipe line (18) and the second bypass exhaust pipe line (19) are connected to at least one conduction separation device (17) arranged upstream of the hydrolysis catalyst (1), wherein the hydrolysis catalyst (1) is arranged in the first bypass exhaust pipe line (18), the second bypass exhaust pipe line (19) bypasses the hydrolysis catalyst (1), wherein in particular the SCR catalyst (2) is arranged downstream of the hydrolysis catalyst (1) and the SCR catalyst (2) is arranged in the first bypass exhaust pipe line (18), and the second bypass exhaust pipe line (19) bypasses the SCR catalyst (2); and / or - Guiding at least a part of the exhaust gas to the hydrolysis catalyst (1). - Preferably controlled according to the measured NO x value, temperature and / or engine load, the throughput of the first conductive exhaust pipe line (12) and the second conductive exhaust pipe line (13), wherein the first conductive exhaust pipe line (12) and the second conductive exhaust pipe line (13) are connected to at least one conductive separation device (11) provided downstream of the hydrolysis catalyst (1), and wherein the SCR catalyst (2) is provided in the first conductive exhaust pipe line (12), and the second conductive exhaust pipe line (13) bypasses the SCR catalyst (2).

14. A method for reducing NO in an internal combustion engine, preferably as claimed in claim 12. x The method for emission, wherein the internal combustion engine is preferably the internal combustion engine according to claim 11, wherein the method Comprising the following steps: - Discharging exhaust gas through the outlet (7) of the cylinder (21); - Guiding the exhaust gas through the hydrolysis catalyst (1); - Guiding the exhaust gas through the SCR catalyst (2) provided downstream of the hydrolysis catalyst (1). wherein - For reducing a given amount of NO x The total volume (V t ) of the hydrolysis catalyst (1) and the SCR catalyst (2) is less than the volume of the separate SCR catalyst (2) for reducing a given amount of NO x , preferably, the total volume of the hydrolysis catalyst (1) and the SCR catalyst (2) is less than 500 l / MW, preferably 400 l / MW and / or - The vanadium content of the SCR catalyst (2) is equal to or greater than 0.3%, preferably equal to or greater than 0.5%, more preferably equal to or greater than 0.7%. and / or - The hydrolysis catalyst (1) and the SCR catalyst (2) are configured to preferably make the residence time of the exhaust gas in the SCR catalyst (2) less than 0.5 seconds, preferably less than 0.3 seconds, when the engine load is at least 90% and / or the exhaust gas mass flow rate is 2 to 20 kg / kWh, preferably 7 to 11 kg / kWh. and / or - The hydrolysis catalyst (1) and the SCR catalyst (2) are provided on the same catalyst substrate (3).

15. The method according to any one of claims 12 to 14, the method comprising the step of measuring the NO x content in the exhaust gas.

16. The method according to claim 15, the method comprising the step of comparing the measured NO x content with a reference value.

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